1. Functions of Bone Structural Mineral Storage Support Protection
Movement
Mineral Storage
Calcium
Phosphate

2. Skeletal Problems Disease / genetics Hormone ablative therapy
Osteoporosis (Type I)
Multiple myeloma
Metastatic bone cancer
Rheumatoid arthritis
Paget’s Disease
Hormone ablative therapy
Spinal cord or nerve injury
Surgery and rehabilitation
Aging (Type II Osteoporosis)
Bedrest
Microgravity

3. Bone Bone composition Two major types of bone Four types of cells
70% mineral (Ca2+ and PO4- as hydroxyapatitie)
22% protein (95% Type I collagen + 5% proteoglycans and other materials)
8% water
Two major types of bone
Compact (cortical, i.e., long bones)
Mechanical and protective functions
Cancellous (spongy, i.e., vertebrae)
Metabolic regulation of calcium
Four types of cells
Osteoblasts
Osteoclasts
Osteocytes
Bone lining cells

4. Bone Cell Types Osteoblasts Osteoclasts Osteocytes Bone Lining Cells
Matrix formation
Secretes Type I collagen
Regulates mineralization
Positioned above osteoid matrix
Matrix usually polarized but can surround cells
Differentiates to become osteocyte
Digests bone
Large multi-nucleated
Exhibits ruffled border and clear zone
Exhibits polarity with nuclei away from bone surface
High density of Golgi stacks, mitochondria and lysozomal vesicles
Born from osteoblasts
Maintains bone matrix
Occupies lucunae
Extends filopodia through canaliculi
Forms gap junctions with neighboring cells
Flat, elongated cells
Generally inactive
Cover surfaces of inactive bone
Thought to be precursor cells to osteoblasts

7. Metabolic Bone Diseases
Osteosclerosis
Osteolysis
Osteoporosis is the most common metabolic bone disease

8. Vertebral Body
Normal
Osteoporotic

9. Definition of Osteoporosis
A systemic skeletal disease
- characterized by low bone mass microarchitectural deterioration of bone tissue
- with a consequent increase in bone fragility and susceptibility to fracture

10. Osteoporosis 1. Low bone mass and 2. Reduced bone quality
Result: Increased risk of fracture